Vacuum flask



FIG. 1 is a perspective view of a vacuum flask, showing my new design;

FIG. 2 is a front view thereof, the rear view being a mirror image of FIG. 2;

FIG. 3 is a left view thereof;

FIG. 4 is a right view thereof;

FIG. 5 is a top view thereof;

FIG. 6 is a bottom view thereof; and,

FIG. 7 is a cross-sectional view, taken along cut-lines 7-7 of FIG. 3.

The broken lines shown in FIG. 3 depict the cut-line of the sectional view of FIG. 7 and form no part of the claimed design.

The broken lines in FIG. 7 show portions of the vacuum flask that form no part of the claimed design. 

CLAIM The ornamental design for a vacuum flask, as shown and described. 